Assisted reproduction technology (ART) procedures typically require treatment with exogenous gonadotropins to stimulate growth and maturation of the ovarian follicles. When gonadotropins are used to treat anovulatory females, the goal is to replicate the normal menstrual cycle, when a single, dominant follicle matures prior to induction of ovulation. In contrast, for women undergoing in vitro fertilization (IVF), controlled ovarian stimulation (COS) is employed to stimulate the growth and maturation of several ovarian follicles, yielding multiple oocytes, which then are retrieved for use in the IVF procedure.
Despite recent advances in ART, ovarian stimulation through exogenous gonadotropins is not uniformly successful due, in part, to varying individual responses to treatment with gonadotropins. This variability complicates patient management and can result in multiple births and potentially life-threatening complications.
Gonadotropins are secreted by the pituitary gland under the control of hypothalamic gonadotropin-releasing hormone (GnRH). Follicle stimulating hormone (FSH) and luteinizing hormone (LH) are the pituitary hormones essential for follicular maturation (folliculogenesis) and luteinization. FSH is required for follicular recruitment (i.e., the early growth of ovarian follicles) at the beginning of the spontaneous menstrual cycle, and it also supports mid- and late-stage folliculogenesis.
FSH is administered therapeutically to induce folliculogenesis in anovulatory women and women undergoing COS. In traditional ovulatory stimulation methods, FSH is administered throughout treatment until the time that oocytes are retrieved. This continued stimulation by FSH can cause multiple conceptions and the potentially fatal condition, ovarian hyperstimulation syndrome (OHSS). Decreasing the dosage of FSH can reduce the risk of OHSS, but low FSH dosages yield inadequate follicle quantities and thus lower the chances of success in assisted reproduction.
LH functions during all stages of a normal menstrual cycle. LH stimulates the theca cells of the follicle to produce the androgen substrate which is converted into estrogen by the aromatase system in the granulosa cells. During the late stages of follicle maturation, approximately 5 to 7 days before ovulation, large ovarian follicles begin to express LH receptors in granulosa cells, which render those follicles responsive to LH for continued maturation and development. Hillier et al., Mol. Cell Endocrinol. 100:51 (1994), Campbell et al. J. Reprod. Fertil. 117:244 (1999). Next, a mid-cycle surge of LH triggers the final stage of follicular maturation and ovulation in a normal menstrual cycle. Ovulation follows the mid-cycle LH surge within 24 to 48 hours. Finally, in the second part of the menstrual cycle, the luteal phase, LH stimulated production of estrogen and progesterone in the corpus luteum of the ovary prepares the uterus for implantation and pregnancy.
In ovarian stimulation protocols, hCG can serve as a source of LH activity because hCG and LH act through the same receptor. Filicori et al. Human Reprod. 17:2009 (2002a); Martin et al., Fertil. Steril. 76: O-49 (2002). Relative to LH, hCG has a longer half-life and, hence, is more potent than LH, although the literature tends to treat hCG and LH as fungible. Indeed, the scientific literature generally does not mention determining the source of LH activity in naturally-derived gonadotropin preparations. But see Filicori et al., Human Reprod. Update 8: 543, 552 (2002b) (“likely hCG content of [a particular] hMG preparation” extrapolated to be “˜5 IU per ampoule,” such that, “of the 75 IU of LH potency contained in this hMG preparation, about 30 IU are provided by hCG”).
The literature discloses using LH activity or low doses of hCG in combination with FSH throughout ovulatory stimulation, but guidance regarding effective amounts and timing of LH activity supplementation is lacking. For example, the abstract of Martin et al., Fertil. Steril. 76: O-49 (2002), discloses administering 2.5 μg recombinant hCG daily (maintaining serum hCG levels from 1-3 mIU/mL) during ovulatory stimulation. Gordon et al. disclose administering 75 IU FSH with 0, 1, 25, and 75 IU LH activity. Human Reprod. 12 (Suppl. 1): 52 (1997a); ibid.: 53 (1997b).
Published studies disclose administering LH activity, throughout stimulation, at FSH to LH ratios of 150:0, 150:37.5, 150:75, and 150:150. Filicori et al. (2002a). Further, the literature documents supplementing FSH stimulation with 50 IU hCG/day (Filicori et al., J. Clin. Endocrinol. & Metabol. 84: 2659 (1999)), and protocols in which 150 IU FSH is administered for 7 days, followed by treatment with FSH-to-hCG ratios of 150:0, 50:50, 25:100, and 0:200 (ibid. 87:1156 (2002c)).
The literature documents other compositions that contain both FSH and LH activity, as well as use of FSH in combination with LH activity. For example, PCT application WO 00/67778, published Nov. 16, 2000, is directed to using LH or an equivalent amount of hCG in combination with FSH to induce folliculogenesis in anovulatory women. More particularly, the '778 application discloses administering LH or “a biologically-active analogue thereof” in doses of 100 to 1500 IU per day (page 4, lines 26-29) and in FSH:LH ratios that range from 1:1.5 to 1:20 (id., lines 16-18).
U.S. Pat. No. 5,929,028 is directed to liquid formulations that contain one or more natural or recombinant gonadotropins, including FSH, LH, and hCG. The '028 patent discusses naturally derived compositions of human menopausal gonadotropin (hMG), which have FSH and LH activities in a ratio of approximately 1:1, but mentions no ratio of FSH to LH activity other than the 1:1 ratio of commercial hMG preparations.
Additionally, there are commercial formulations that contain both FSH and LH. Human-derived preparations are available containing 75 IU FSH with 75 IU LH activity (Pergonal, Humegon, Menogon, Repronex, and Menopur) and 75 IU FSH with 25 or 35 IU LH activity (Normegon and Pergogreen).
It is conventional wisdom, however, that “excessive” LH levels, albeit ill-defined, result in follicular atresia, suppression of granulosa cell proliferation, and premature luteinization. See, generally, Filicori, Fertil. Steril. 79: 253 (2003). Although recent work suggests otherwise, a notion persists in the field that LH activity levels must be within a certain range, and that levels below or above an “LH ceiling” impair normal follicle development. Shoham, Fertil. Steril. 70: 1170 (2002).
In summary, there is published evidence that supplementing FSH with LH activity during ovulation induction reduces the duration of treatment and the amount of gonadotropin used to achieve proper follicle development. Filicori et al. (1999), (2002b). On the other hand, the belief persists that “high” LH activity levels negatively impacts follicle development.
That belief has guided the conventional ovarian-stimulation paradigm, which involves administration of FSH throughout controlled ovarian stimulation. Exogenous LH activity is deemed unnecessary and even detrimental during the early to middle stages of follicular development. Accordingly, the traditional means of ovarian stimulation entails treatment with FSH alone, typically at 75 IU/day. In this traditional protocol, LH activity is administered to induce ovulation only after the follicle reaches a certain stage of development. Only recently has LH activity been administered throughout treatment, and the optimal amount and timing of LH activity that is effective in this context remains controversial.